Researches of Elastic Elements an ABS-Controller System

Transcription

1 Researches of Elasic Elemens an ABS-Conroller Sysem D.C. THIERHEIMER, L. GACEU, M. CLINCIU, O. CÂMPIAN, D. OLA, W.W. THIERHEIMER Faculy of Food and Tourism Transilvania Universiy of Brasov Eroilor 29, , Brasov ROMANIA Absrac: - Ani-locking brake sysems (ABS) are well esablished in he auomoive indusry as a safey feaure. ABS generally offers superior vehicle safey by limiing he longiudinal wheel slip in a braking even wih deep slip condiion. In his paper is presened a srucure soluion of elasic elemen from elecromagneic valve ha has he roll o reduce he noise and vibraions from brake pedal. A he same ime, his soluion improve he dynamic of ABS regulaor of he vehicle, allowing an increase of frequency of work and, implici he reducing he braking space. Drivers would have beer direcional conrol of he vehicle equipped wih ABS. The performances of consrucive soluion depending on achieving own resonance frequency are presened and confirmed in his paper by means of resuls obained experimenally. Key-Words: diaphragm like elasic elemen, conrol, adjusmen 1 Inroducion In consrucion of braking sysems, beside echnical, funcional and he reliabiliy parameers, mus be aking accoun of he influence of braking on he sabiliy of he vehicle, occupans and goods ranspored [2]. The braking, wih or wihou locking he wheels, is sricly relae o complex sysem driver-vehicleroad-environmen. In consrucion of braking sysems, beside echnical, funcional and he reliabiliy parameers, mus be aking accoun of he influence of braking on he sabiliy of he vehicle, occupans and goods ranspored. The assessmen and comparison of braking qualiy of he vehicles are realized by means of maximum deceleraion boh absolue and relaive, ime and minimum braking space, as funcion of velociy sae of movemen of he wheel. Braking sysem influence he acive safey of he vehicle. Braking process by achieving a minimum of braking space is opimal in he momen when he sideslip of he braked wheel would have he values corresponding o maximum of drag facor 2 Independen adjusmen In figure 1 is presened he main loop of adjusmen for braking sysem wih ABS, from he poin of view of wheel. The longiudinal sideslip of he wheel s ref is replaced by wheel speed ref, bu i may be used anoher variable, who characerize he wheel speed as command parameer. The variable s ref is generaed by he superior sage of ABS adjusmen sraegy, which has he objecive he dynamic behavior of he vehicle during braking [3]. The adjusmen loop, paricular o he wheel, is composed by an ABS auoma regulaor (conroller) wih high dynamiciy, who generae he measures for command, like elecrical signals +u(), -u() for he elecromagneic valves, wih he aim of increasing or decreasing of he pressure in he sysem. Fig. 1 The main loop of adjusmen for braking sysem wih ABS 3 Valve command and braking hydraulic An imporan par of deficiency are eliminaed in he same ime wih echnical-experimenal ISBN:

2 accomplishmens of braking adjusmen, if for he valve command are used signals modulaed by exending in ime of impulse (2) wih consan ac rae. This mehod of command signals generaing is necessary o be able o conrols in real ime he adjusmen by he processor from vehicle compuer. If elecromagneic valves doesn have memory who ransfers he sae informaion beween wo cycles of command-conrol, hen he saionary characerisics of he valves l u mus be perfec valuable, and for ransiory adjusmen signals l, oo. u u u The volage of command measure max lead on increase of he magneic force F M (), who influences he valve opening (). The passing secion is maximum only in he case when magneic force F M surmouns he oughness of he elasic elemen of he valve and anoher force who lead on siing of he mobile elemen on his sea. This is he reason why he opening of he valve ()>0 is realized wih a ime delay i, bu reach quickly his maximum value x max, meanwhile he elecromagneic force F M is sill rising. The response characerisic on he closing sage of he valve, resuls from cuing he command signal u 0, would be disorional and delayed because of ineria, in he same way like he opening sage x() > 0. The relaionship beween acing volage of he valve u() and he passing secion resuling from displacemen of he valve x() are analyzed aking accoun by elecromagneic componens of he valve. Fig. 2 The elecromagneic behavior of he excied valve wih inpu ype signals : l ; 1 1 u l u (1) In his paper, he characerisics of boh elecromagneic valves are included in one funcion l u ; 0 describe he mean opening of he increasing pressure valve (pressurizaion), meanwhile he decreasing pressure valve (depressurizaion) is closed; 0 describe saes of he valve who conduc o reducing he braking pressure. The condiion ha valves reac independen i may be possible by corresponding conceps of command. The characerisic l u may be considered like modeling for he componens of command sysem and also for he dynamic modeling of valve. Bu i mus be aking accoun ha he adjusmens signals ransmissions l u (he measure of conversion command, acing measure, execuion measure) are realized wih delay of an impulse rae. 3.1 The physical modeling of he valve To exemplifying he elecromagneic properies, in figure 2 is presened he ABS valve response from a perurbaion like impulse form wih fixed ime. Fig. 3 The consrucion and dynamic characerisics for he elecromagneic valve wih diaphragm like elasic elemen In figure 3 are represened he consrucion and imporan parameers of he elecromagneic valve, proposed for he ABS sysem. Because of induciviy L V, he elecromagneic force F M () will be reduced in comparison wih command volage u() realized. The ohm resisance R V of solenoid limis he inensiy of he elecrical curren from ISBN:

3 Angular velociy [rev/min] Recen Researches in Circuis, Sysems, Elecronics, Conrol & Signal Processing valve o he maximum limi i max, who is dependen of volage u. The elecromagneic force F M mus surmoun he siffness of he elasic elemen C V of he valve, he fricion forces F R from valve and he cushion and inerial forces who are opposie o he movemen of he acive elemen of closing. The dynamics of opening elecromagneic valve is described by means of a equivalen sysem, elecromechanical, nonlinear of he hydrologisor 3/2 (wo ways and hree posiions). 3.2 The command enabling verifying he model The verificaion of he model described above and qualiy assessmen is more difficul o realize experimenally, because he opening () of he valve imply big financial resources o implemening he sensors. Consider his, I would ry o use an alernaive indirecly mehod, o verify he evoluion of pressures and conrol signals o he valve. The verificaion ess, periodical accomplished, wih he aim of obaining saionary movemen of he valve are designaed o confirm he nonlinear co-operaion of he valve parameers on ransiory perurbaions. So ha, he research is focused on valve command u, aking accoun of varied modulaion of exciaion impulse, bu wih a fixed period of ime from he cycle, see figure 2. * * 1, k ( k ) ; u ( ) 0, în res (2) k 0,1, 2,... l u is he relaive period of exciaion impulse of command ( 0 1). The emporal sages of he l u valve opening () resuled, becomes periodical afer o shor period of reesablishing. If he pressure variaions on he period of cycle is less hen differenial pressure p p0 who ac on he valve, he sae of valve in ha period of ime is considered mean equivalen opening of he valve l u : d ( lu) ( ; lu) 1 k d [ p ( ) p0] (3) k d ()[ p() p0 ] The valve opening () and implici he work secion offered by he opening is due by l u command and offer ogeher wih he ransfer characerisic l u generaed from differen values of l u, an exacly descripion of he properies of he elecromagneic valve. 4 Experimenal analysis The closing and opening imes of he elecromagneic valve depend on he commuing mode, pressure, he necessary flow used in braking process, depend also wih liquid emperaure. These imes may be modified by changing he characerisic of elasic elemen, he work secion, ec. The sealing up from he rod and he cap piece of he elecromagneic valve is realized wih special adhesive and O-ring elemen, o eliminae he influence on he dynamics of commuing process. The pieces in movemen was carefully accomplished (rod coupling mobile elemen, cylinder bore ac elemen sensor). To increase he area of experimens, is used he exernal command of he elecromagneica valve by means of Bosch module, from a source wih consan pressure (he pump P 1 ). This soluion allows o convenien variaion of braking pressure p, independen from main source of hydraulic energy P 2. Vehicle and wheel velociy Time [s] Fig. 4 Tesing resuls Wheel velociy Vehice velociy The displacemen of he mobile elemen of he elecromagneic valve was racing by means of ransducer, personal realizaion, who conain a rod solidary wih he ransducer and wih anoher rod from an inducive ransducer of displacemen. The sealing up from he rod and he cap piece of he elecromagneic valve is realized wih special adhesive and O-ring elemen, o eliminae he influence on he dynamics of commuing process. The pieces in movemen was carefully accomplished ISBN:

4 (rod coupling mobile elemen cylinder bore ac elemen sensor). The charge wih work fluid is realized by hydraulic resisance d 1, wih 1.5 mm diameer. The discharge of work fluid is made by resisance wih adjusable secion. For he proposed elecromagneic valve, he forces of liquid je for a cerain displacemen of he mobile elemen, beween 0 1 mm have a maximum. For hese reason he resulan force on he mobile elemen increases o he end of displacemen of he closing even. For he opening even, noice he small dependency from siffness of he elasic elemen. If consider he closing even, i may be noiced a clearly reducion of ha, ogeher wih increasing he force of spring. This is he resul of imporance of he spring forces, noiced above, in closing process, represening a he beginning an imporan par from main forces for he acceleraion phase of he mobile elemen. As a resul form esing he sysem, is obained he nex characerisic, fig. 4, 5. Closing Opening Fig. 5 Tesing resuls 5 Conclusion These soluions proposed for elasic elemen consrucion is realized for increased of efficiency of braking process. Frequenly, besides commuaion funcions of elasic elemens, like closing mainains of elecromagneic forces, he opening forces due ha, will be done by corresponding choice of siffness of elasic elemen. Anoher essenial influence is made by force from elasic elemen, in he closing ime. The values of he forces effec on valve acceleraion, realizing he poin of ime of beginning and developmen of closing process. Beween mobile elemen and ha guide is he coulombian fricion (solid body fricion) and Newonian fricion. Boh forces are oriened conrary o he sense of movemen. The jamming force of he mobile elemen due o non-corresponding form and he forces who ac following he preension of valve guide are normal forces which induce dry fricion. By corresponding execuion, hese forces may be mainained o he small values, which are negleced. The Newonian fricion is due from mobile elemen and valve guide, and is velociy and is velociy funcion of he mobile elemen and from clearance. These forces, by comparison wih hydraulic ones, are small, like coulombian forces, and for a-priori deerminaion of commuing ime, hese may be negleced. Time hisory of valve displacemen having basics on he opening/closing mechanism induces obviously differences. Of big imporance for dynamic behavior of elecromagneic valve individually commanded is he choosing of acing, and from ha, he pressure force on he surface of he mobile elemen and reacion forces of he liquid je. In commuaion process exiss also he spring forces, fricion forces and Newonian an coulombian forces. In he same ime wih inerpreaion of he funcioning elecromagneic valve is possible o correlae he command signals l u o induce an opimal dynamic of he flowing, aking accoun of ha i may be resumed ha, in he generally sysem, may be obained own frequency, relaively high, beween 7 15 Hz in dynamic analysis of he componen elemens of ABS sandard, and lile delays and dead imes from adjusmen loop of braking are imporan, aking accoun of hese only in funcioning wih perurbaions from ouside or inside. These will esablish he limi ampliudes of he adjusmen loops aking accoun of unsable mechanical condiions ha appear in he momen of exceeded of bending forces. To obaining an improved qualiy facor of he adjusmen process, mus be accomplished he condiion of fulfill he high own frequency, in his way all he componens of he adjusmen loop mus be opimized, from own characerisic speaking, referring o he dead imes generaing. References: [1] Thierheimer, W. The heory of ehnical sysems of agriculure and food indusry, Transilvania ISBN:

5 Universiy of Brasov Publishing House, ISBN X, [2] Thierheimer, W.; Tane, N.; Thierheimer, D.; (2008) Sudies concernering he rolling moion reducion by conrolling he seering and gear and he spring rigging correlaion, In: Annals of DAAAM for 2008 & Proceedings of he 19h Inernaional DAAAM Symposium, Kaalinic, B. (Ed.), pp , ISBN , ISSN , Published by DAAAM Inernaional, Vienna. [3] Thierheimer, W.; Gaceu, L.; Thierheimer, D., Ardeleanu, D., Analysis of Elasic Elemens Conained in he ABS-Conroller, In: Recen Advances in Applied and Theoreical Mechanics, Proceedings of he 5h WSEAS Inernaional Conference on Applied and Theoreical Mechanics, Puero De La Cruz, Tenerife, Spain, December 14-16, 2009, pp , ISBN , ISSN , Published by WSEAS Press. ISBN: